Reducing signature matching uncertainty in media monitoring systems

ABSTRACT

Methods, apparatus, systems and articles of manufacture to reduce signature matching uncertainty in media monitoring systems are disclosed. Disclosed example apparatus are to compare first groups of monitored signatures representative of monitored media with second groups of reference signatures representative of respective reference media to determine a first sequence of match results for an observation period, the first and second groups to have a first size corresponding to a first number of signatures. Disclosed example apparatus are also to compare, in response to a discontinuity in the first sequence of signature match results, third groups of monitored signatures from the sequence of monitored signatures with fourth groups of reference signatures from the respective sequences of reference signatures to determine a second sequence of signature match results for the observation period, the third groups and the fourth groups to have a second size greater than the first size.

RELATED APPLICATION(S)

This patent arises from a continuation of U.S. patent application Ser.No. 16/417,140 (now U.S. Pat. No. 10,931,987), which is entitled“REDUCING SIGNATURE MATCHING UNCERTAINTY IN MEDIA MONITORING SYSTEMS,”and which was filed on May 20, 2019, which is a continuation of U.S.patent application Ser. No. 15/894,671 (now U.S. Pat. No. 10,321,171),which is entitled “REDUCING SIGNATURE MATCHING UNCERTAINTY IN MEDIAMONITORING SYSTEMS,” and which was filed on Feb. 12, 2018, which is acontinuation of U.S. patent application Ser. No. 14/947,876 (now U.S.Pat. No. 9,900,636), which is entitled “REDUCING SIGNATURE MATCHINGUNCERTAINTY IN MEDIA MONITORING SYSTEMS,” and which was filed on Nov.20, 2015, which claims the benefit of U.S. Provisional Application Ser.No. 62/205,436, which is entitled “RESOLVING MULTIPLE MATCH CONDITIONSIN AUDIO FINGERPRINT ANALYSIS,” and which was filed on Aug. 14, 2015.Priority to U.S. patent application Ser. No. 16/417,140, U.S. patentapplication Ser. No. 15/894,671, U.S. patent application Ser. No.14/947,876, and U.S. Provisional Application Ser. No. 62/205,436 isclaimed. U.S. patent application Ser. No. 16/417,140, U.S. patentapplication Ser. No. 15/894,671, U.S. patent application Ser. No.14/947,876, and U.S. Provisional Application Ser. No. 62/205,436 arehereby incorporated by reference in their respective entireties.

FIELD OF THE DISCLOSURE

This disclosure relates generally to media monitoring and, moreparticularly, to reducing signature matching uncertainty in mediamonitoring systems.

BACKGROUND

A media monitoring system typically includes one or more device metersto monitor the media presented by one or more media devices located atone or more monitored sites. In some example media monitoring systems,media signatures are collected by the device meters and used to identifyand/or otherwise monitor the media presented by the one or moremonitored media devices. Unlike media monitoring techniques based oncodes and/or watermarks included with and/or embedded in the monitoredmedia, signature-based media monitoring techniques generally use one ormore inherent characteristics of the monitored media measured over amonitoring time interval to generate a substantially unique proxy torepresent the media. Such a proxy is referred to as a media signature ormedia fingerprint, and can take any form (e.g., a series of digitalvalues, a waveform, etc.) representative of any aspect(s) of themonitored media signal(s) (e.g., the audio and/or video signals formingthe media presentation being monitored). A good media signaturegeneration algorithm is typically one that generates repeatablesignatures from the same media presentation, but generates uniquesignatures relative to other (e.g., different) presentations of other(e.g., different) media.

When signatures are used for media monitoring, signatures of themonitored media (referred to herein as monitored signatures) aregenerated by the device meter and compared to reference signaturesrepresentative of reference media known to the media monitoring system.When a match is found, the media corresponding to the monitoredsignatures being processed can be identified as corresponding to thereference media represented by the matching reference signatures. Inmany media monitoring systems, the device meters provide their generatedsite signatures to a data processing facility or other centralizedprocessing site for comparison with the reference signatures that arerepresentative of the reference media available for presentation at therespective monitored sites.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example media monitoring system capableof reducing signature matching uncertainty in accordance with theteachings of this disclosure.

FIG. 2 is a block diagram of an example monitored site that may bemonitored by an example site monitor included in the example mediamonitoring system of FIG. 1.

FIG. 3 is a block diagram of an example reference identification systemthat may be included in the example media monitoring system of FIG. 1.

FIGS. 4A-B illustrate example media signatures that may be generated bythe example site monitor(s) and the example reference identificationsystem included in the example media monitoring system of FIG. 1.

FIG. 5 is a block diagram of a first example implementation of anexample crediting facility that may be included in the example mediamonitoring system of FIG. 1.

FIG. 6 illustrate example an example analysis window capable of beingused by the example crediting facilities of FIGS. 1, 5 and/or FIG. 9 toreduce signature matching uncertainty in accordance with the teachingsof this disclosure.

FIG. 7 illustrates example matching results for a sequence of monitoredsignature packets using a first analysis window.

FIG. 8 illustrates example matching results for a sequence of monitoredsignature packets using a second analysis window that is larger than thefirst analysis window.

FIG. 9 is a block diagram of a second example implementation of anexample crediting facility that may be included in the example mediamonitoring system of FIG. 1.

FIG. 10 is a flowchart representative of example machine readableinstructions that may be executed to implement the first examplecrediting facility of FIG. 5.

FIG. 11 is a flowchart representative of example machine readableinstructions that may be executed to implement the second examplecrediting facility of FIG. 9.

FIG. 12 is a flowchart representative of example machine readableinstructions that may be executed to implement uncertainty detectionprocessing for the first example crediting facility of FIG. 5 and/or thesecond example crediting facility of FIG. 9.

FIG. 13 is a block diagram of an example processor platform structuredto execute the example machine readable instructions of FIGS. 10 and/or12 to implement the first example crediting facility of FIG. 5.

FIG. 14 is a block diagram of an example processor platform structuredto execute the example machine readable instructions of FIGS. 11 and/or12 to implement the second example crediting facility of FIG. 9.

The figures are not to scale. Wherever possible, the same referencenumbers will be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts, elements, etc.

DETAILED DESCRIPTION

Methods, apparatus, systems and articles of manufacture (e.g., physicalstorage media) to reduce signature matching uncertainty in mediamonitoring systems are disclosed herein. Example media monitoringmethods disclosed herein include executing a media signature matchingprocedure using a first analysis window on monitored media signaturesrepresentative of monitored media to identify the monitored media. Suchdisclosed example methods also include, in response to determining firstmatching results obtained from executing the media signature matchingprocedure using the first analysis window are indicative of a matchinguncertainty condition, outputting second matching results obtained fromexecuting the media signature matching procedure on the monitored mediasignatures using a second analysis window. In some such examples, thesecond analysis window is larger than the first analysis window. Forexample, the first analysis window may be substantially equal to four(4) seconds (or some other value), and the second analysis window may besubstantially equal to thirty-two (32) seconds (or some other value).

Some disclosed example methods further include outputting the firstmatching results obtained from executing the media signature matchingprocedure using the first analysis window in response to determining thefirst matching results are not indicative of the matching uncertaintycondition. For example, some such disclosed example methods includeexecuting the media signature matching procedure using the firstanalysis window in parallel with executing the media signature matchingprocedure using the second analysis window. Some such disclosed examplemethods also include switching between outputting the first matchingresults obtained from executing the media signature matching procedureusing the first analysis window and outputting the second matchingresults obtained from executing the media signature matching procedureusing the second analysis window depending on whether the first matchingresults are indicative of the matching uncertainty condition.

Additionally or alternatively, some disclosed example methods furtherinclude examining, over a first observation period, reference timestampsassociated with consecutive ones of the first matching results obtainedfrom executing the media signature matching procedure using the firstanalysis window. Some such disclosed example methods also includedetermining the first matching results are indicative of the matchinguncertainty condition when the reference timestamps are discontinuous inthe first observation period. Some such disclosed example methodsdetermine the reference timestamps are discontinuous in the firstobservation period when, over the first observation period, successiveones of the reference timestamps do not increment relative to precedingones of the reference timestamps by a first amount within a range basedon a time resolution associated with the first matching results.

Additionally or alternatively, in some disclosed examples, a first oneof the first matching results is determined by comparing a first groupof monitored signatures spanning a duration corresponding to the firstanalysis window to respective groups of reference signaturesrepresentative of respective different reference media sources todetermine respective signature comparison values corresponding to thedifferent reference media sources. Some such disclosed example methodsfurther include determining the first matching results are indicative ofthe matching uncertainty condition when the first one of the firstmatching results indicates multiple reference media sources haverespective signature comparison values that satisfy a comparisonthreshold.

These and other example methods, apparatus, systems and articles ofmanufacture (e.g., physical storage media) to reduce signature matchinguncertainty in media monitoring systems are disclosed in further detailbelow.

As mentioned above, in media monitoring systems employing mediasignatures, monitored media signatures generated by device meters arecompared to reference signatures representative of reference media knownto the media monitoring system. When a match is found, the mediacorresponding to the monitored signatures being processed can beidentified as corresponding to the reference media represented by thematching reference signatures. However, prior media monitoring systemscan be prone to signature matching uncertainty when, for example, thesame monitored media can be associated with multiple different referencesources.

For example, a given thirty (30) second commercial advertisement may becontracted to air on several different television channels at severaldifferent times of the day and/or on several different days of a givenweek. In such an example, the media monitoring system may consider thedifferent possible televisions channels to be different possiblereference media sources represented by respective sets of referencemedia signatures. However, because the media making up the commercial isthe same for each possible airing of the commercial, the monitored mediasignatures obtained from a presentation of this commercial received by amonitored media device on a first one of these channels (e.g.,corresponding to a first reference source) at a first time of day maymatch the respective reference media signatures representative of someor all of the other airings of this commercial at other times on thissame channel (e.g., corresponding to the same first reference source),and/or at the same time and/or at other times on the other channels(corresponding to the other possible references sources). Prior mediamonitoring systems may be unable to resolve such signature matchinguncertainty resulting from (1) multiple potential reference mediasources having reference signatures capable of matching a given group ofmonitored media signatures and/or (2) the same reference media sourcehaving multiple different groupings of reference signatures capable ofmatching the given group of monitored media signatures.

Unlike such prior media monitoring systems, example media monitoringsystems disclosed herein are able to resolve signature matchinguncertainty resulting from (1) multiple potential reference mediasources having reference signatures capable of matching a given group ofmonitored media signatures and/or (2) the same reference media sourcehaving multiple different groupings of reference signatures capable ofmatching the given group of monitored media signatures. Morespecifically, example media monitoring systems disclosed herein utilizemultiple analysis windows to resolve such signature matchinguncertainty. Prior media monitoring systems typically utilize oneanalysis window, which defines the size of the group, or neighborhood,of media signatures to be compared to determine whether monitored mediamatches a particular reference media source. Because media signaturesare generated at successive signature generation time intervals (e.g.,16 millisecond intervals or some other value), the analysis window alsodefines the durations of the media segments which are compared todetermine whether monitored media matches a particular reference mediasource. The analysis window utilized by such prior media monitoringsystems is usually chosen to be short enough (e.g., 4 seconds or someother value) to ensure that the signatures included in the group, orneighborhood, of monitored media signatures defined by the analysiswindow belong to the same monitored media segment. However, if the samemonitored media segment can be obtained from multiple, differentreference media sources (such as in the example above), and/or atdifferent times from the same reference media source, the group, orneighborhood, of monitored media signatures included in this shortanalysis window will likely match some or all of these different groupsof reference signatures, thereby resulting in the signature matchinguncertainty problem illustrated above.

Disclosed example media monitoring systems utilize multiple analysiswindows to provide a technical solution to solve the technical problemof signature matching uncertainty. For example, and as disclosed infurther detail below, media monitoring systems employing multipleanalysis windows in accordance with the teachings of this disclosure canuse a short analysis window (e.g., of 4 seconds or some other value) tocompare monitored and reference signatures until a signature matchinguncertainty condition is detected. Then, upon detecting the signaturematching uncertainty condition, disclosed example media monitoringsystems can switch to using a long analysis window (e.g., of 32 secondsor some other value) to resolve the signature matching uncertaintycondition. In some examples, the long analysis window is chosen to havea duration longer than a media segment of interest (e.g., longer than a30 second commercial), which causes the group, or neighborhood, ofmonitored media signatures included in the long analysis window to spanmultiple media segments (e.g., such as multiple commercials, or acommercial and a television program, etc.). In general, the combinationof successive media segments available to a monitored media device at agiven time-of-day and day-of-week will be unique to a given referencemedia source (e.g., corresponding to a given television channel on agiven day and at a given time-of-day).

As such, using a long analysis window when signature matchinguncertainty conditions are detected can help resolve such uncertainties,thereby allowing the unique reference media source corresponding to themonitored media to be accurately identified. However, when signaturematching uncertainty conditions are not detected, disclosed examplemedia monitoring systems can switch to utilizing a short analysiswindow, which supports finer signature matching granularity, therebyenabling channel surfing and similar media consumption behaviors to bemonitored accurately. Examples techniques for reliably detectingsignature matching uncertainty conditions are disclosed in furtherdetail below.

Turning to the figures, a block diagram of an example media monitoringsystem 100 capable of reducing signature matching uncertainty inaccordance with the teachings of this disclosure is illustrated inFIG. 1. The example media monitoring system 100 of FIG. 1 includes oneor more example site monitor(s) 105 to monitor media presented at one ormore monitored sites. In the illustrated example of FIG. 1, the media tobe monitored is distributed by one or more example media distributor(s)110. A media distributor 110 can correspond to any type of mediadistributor, such as a television station, a cable network, a satellitenetwork (e.g., television or radio), a radio station, a streaming mediaservice (e.g., such as Hulu™, Netflix®, etc.), etc. As such, the mediadistributed by the media distributor(s) 110 can correspond to any typeof media, such as television programming, radio programming, multimedia(e.g., audio and/or visual) data, etc. In the illustrated example, themedia distributor(s) 110 can distribute a particular piece/segment ofmedia (e.g., such as a particular television program, a particular radioprogram, a particular movie, a particular commercial, etc.) torecipients (e.g., television viewers, radio listeners, computer users,electronic device users, etc.) via one or more example distributionmedia 115 (e.g., such a one or more radio frequency, cable and/orsatellite television and/or radio channels, one or more networkscarrying one or more digital transport channels, etc.).

In the example media monitoring system 100 of FIG. 1, the mediadistributor(s) 110 distribute media via the distribution media 115 toone or more monitored sites, which are monitored by the example sitemonitor(s) 105. In some examples, the monitored sites correspond to oneor more panelists selected (e.g., statistically) for inclusion in anaudience measurement panel, media monitoring survey, etc. In someexamples, each monitored site includes one or more media devices topresent the media received at the monitored site from the mediadistributor(s) 110. In the illustrated example of FIG. 1, a givenmonitored site may be associated with one or more of the example sitemonitors 105. As discussed in further detail below, an example sitemonitor 105 for a given monitored site includes one or more devicemeter(s) to monitor the media presented by the media device(s) at themonitored site. For example, a device meter included in an example sitemonitor 105 can determine metering data, such as media signatures, thatmay be used to identify (and, thus, infer exposure to) media presentedby a media device. In some examples, a site monitor 105 also includes apeople meter to determine audience identification data (also referred toas demographic data, people meter data, etc.) identifying the audiencemembers (e.g., panelists) being exposed to the monitored media, and/orin the vicinity of the monitored media device, etc. In such examples,the site monitor 105 for a given monitored site combines the meteringdata with the audience identification data to determine audiencemeasurement data characterizing media exposure at the monitored site.The site monitor 105 can then store and report the metering data (oraudience measurement data) to an example crediting facility 120 via anexample reporting medium 125. In the illustrated example, the reportingmedium 125 can be any type of data transmission medium, such as one ormore data networks (e.g., such as the Internet), one or more mobiletelephone (e.g., cellular) networks, a dial-up connection, etc. Anexample implementation of a site monitor 105 is illustrated in FIG. 2,which is described in greater detail below.

In the media monitoring system 100 of the illustrated example, thecrediting facility 120 performs signature matching for media monitoring.Moreover, the example crediting facility 120 implements exampletechniques to reduce signature matching uncertainty in accordance withthe teachings of this disclosure. Unlike media monitoring based on codesand/or watermarks included with and/or embedded in the monitored media,signature-based media monitoring generally uses one or more inherentcharacteristics of the monitored media during a signature samplinginterval to generate a substantially unique proxy for the media. Such aproxy is referred to as a signature or media fingerprint, and can takethe form of a series of bits, data values, a waveform, etc.,representative of the media signal(s) (e.g., an audio signal and/or avideo signal) forming the media presentation being monitored. A goodsignature is usually one that is repeatable when processing the samemedia presentation, but that is unique relative to other (different)presentations of other (different) media. Thus, as used herein, asignature is a representation of some characteristic of the media signal(e.g., a characteristic of the frequency spectrum of the signal) whichcan be used to identify the signal, and can be thought of as afingerprint. Signatures are typically not dependent upon insertion ofidentification codes in the media, but instead preferably reflect aninherent characteristic of the media and/or the signal transporting themedia. Systems to utilize codes and/or signatures for audiencemeasurement are long known. See, for example, Thomas, U.S. Pat. No.5,481,294, which is hereby incorporated by reference in its entirety.

In the example media monitoring system 100 of FIG. 1, signature-basedmedia monitoring generally involves a site monitor 105 determining(e.g., generating) monitored signature(s) (also referred to as collectedsignature(s) or site signature(s)) representative of a media signal(e.g., an audio signal and/or a video signal) output by a media devicemonitored by the site meter 105. The site monitor 105 includes themonitored signature(s) in the metering data reported to the examplecrediting facility 120. The crediting facility 120 then compares themonitored signature(s) to one or more references signaturescorresponding to known (e.g., reference) media. Various comparisoncriteria, such as a cross-correlation value, a Hamming distance,population (POP) count, etc., can be evaluated to determine whether agroup, or neighborhood, of monitored signatures matches a particulargroup, or neighborhood, of reference signatures. When a match betweenthe monitored signatures and the reference signatures is found, themonitored media represented by the monitored signatures can beidentified as corresponding to the particular reference mediarepresented by the reference signatures that matched the sitesignatures. Because attributes, such as an identifier of the media, apresentation time, a broadcast channel, etc., are collected and, thus,known for the reference media represented by the matching referencesignatures, the crediting facility 120 may associate the monitored mediawith these same attributes of the matching reference media. Thecrediting facility 120 can then use the identified attributes of themonitored media to perform any appropriate post-processing to, forexample, determine audience ratings information, identify targetedadvertising to be provided to a site monitored by the site monitor 105that reported the monitored signatures, etc.

The crediting facility 120 of the illustrated example also employsexample techniques disclosed herein to resolve, or at least reduce,signature matching uncertainty resulting from (1) multiple potentialreference media sources having reference signatures capable of matchinga given group of monitored media signatures and/or (2) the samereference media source having multiple different groupings of referencesignatures capable of matching the given group of monitored mediasignatures. As disclosed in further detail below, the example creditingfacility 120 utilizes multiple analysis windows to resolve suchsignature matching uncertainty. In the example of FIG. 1, the creditingfacility 120 defaults to using short analysis window (e.g., of 4 secondsor some other value) to define the groups, or neighborhoods, ofmonitored and reference signatures to be compared to identify areference source that matches the monitored media. The creditingfacility 120 of the illustrated example continues to use the shortanalysis window to compare monitored and reference signatures until asignature matching uncertainty condition is detected. Then, upondetecting the signature matching uncertainty condition, the creditingfacility 120 of the illustrated example switches to using a longanalysis window (e.g., of 32 seconds or some other value) to resolve thesignature matching uncertainty condition.

In some examples, the long analysis window is chosen to have a durationlonger than a media segment of interest (e.g., longer than a 30 secondcommercial), which causes the group, or neighborhood, of monitored mediasignatures included in the long analysis window to span multiple mediasegments (e.g., such as multiple commercials, or a commercial and atelevision program, etc.). In general, the combination of successivemedia segments available to a monitored media device at a giventime-of-day and day-of-week will be unique to a given reference mediasource (e.g., corresponding to a given television channel on given dayand at a given time-of-day). As such, the example crediting facility 120uses the long analysis window when signature matching uncertaintyconditions are detected to resolve, or at least reduce, suchuncertainties, thereby allowing the unique reference media sourcecorresponding to the monitored media to be accurately identified.However, when signature matching uncertainty conditions are notdetected, the example crediting facility 120 can switch to utilizing theshort analysis window, which supports finer signature matchinggranularity, thereby enabling channel surfing and similar mediaconsumption behaviors to be accurately monitored. Operation of thecrediting facility 120 to reduce signature matching uncertainty isdescribed in further detail below in connection with the exampleimplementations of the crediting facility 120 illustrated in FIGS. 5-9.

The example media monitoring system 100 of FIG. 1 also includes anexample reference identification system 130 to generate some or all ofthe reference signatures used by the example crediting facility 120. Asdescribed in further detail below, in some examples, the referenceidentification system 130 is located separately from the site monitor(s)105 and monitors media distributions by some or all of the example mediadistributor(s) 110. The reference identification system 130 determinesreference signatures from the media distributions, which correspond tothe possible media that could be received at the monitored site(s)monitored by the example site monitor(s) 105. For example, for eachmedia distribution monitored by the reference identification system 130,the reference identification system 130 generates respective referencesignatures (e.g., sets/sequences of reference signatures representativeof the different media distributions and associated with a signaturemonitoring interval), timestamps the reference signatures with timeinformation (e.g., such as day and/or time-of-day information)corresponding to when the distributed media was received at thereference identification system 130, and associates media identificationinformation with the reference signatures. The reference identificationsystem 130 then stores and reports the timestamped reference signaturesand media identification information to the crediting facility 120 viaan example reporting medium 135. In the illustrated example, thereporting medium 135 can be any type of data transmission medium, suchas one or more data networks (e.g., such as the Internet), one or moremobile telephone (e.g., cellular) networks, a dial-up connection, etc.An example implementation of the reference identification system 130 isillustrated in FIG. 3, which is described in greater detail below.

A block diagram of an example implementation of one of the site monitors105 of FIG. 1 is illustrated in FIG. 2. The example site monitor 105 ofFIG. 2 monitors an example media device 205 (also referred to herein asa media presentation device 205) that is to present media received at amonitored site via the distribution medium 115. The media device 205 cancorrespond to any type of media device, such as a set-top box, atelevision, a radio, a multimedia computer system, tablet computer, aportable digital assistant, a cellular/mobile smartphone, etc. In someexamples, the media device 205 is capable of directly presenting media(e.g., via a display) while, in other examples, the media device 205presents the media on separate media presentation equipment (e.g.,speakers, a display, etc.). Thus, as used herein, media devices may ormay not be able to present media without assistance from a seconddevice.

The example site monitor 105 of FIG. 2 includes an example device meter210, also referred to as a meter 210, a site meter 210, a site unit 210,a home unit 210, a media meter 210, etc., to monitor media presented bythe media device 205. In the illustrated example, the media monitored bythe device meter 210 can correspond to any type of media presentable bythe media device 205. For example, monitored media can be media content,such a television programs, radio programs, movies, etc., and/orcommercials, advertisements, etc. As such, the term “media” includes anytype of content and/or advertisement delivered via any type ofdistribution medium. Thus, media includes television programming oradvertisements, radio programming or advertisements, movies, web sites,streaming media, etc.

In the illustrated example, the device meter 210 determines meteringdata that may identify and/or be used to identify media presented by themedia device 205, which may be used to thereby infer media exposureand/or consumption at the monitored site. The metering data determinedby the example device meter 210 includes site signatures representativeof the media presented by the media device 205. For example, in the sitemonitor 105 of FIG. 2, the device meter 210 may utilize invasivemonitoring involving one or more physical connections to the mediadevice 205, and/or non-invasive monitoring not involving any physicalconnection to the media device 205, to obtain access to one or moremedia signals corresponding to the media being presented by the mediadevice 205. In some examples, the device meter 210 may process audiosignals obtained from the media device 205 via a microphone and/or otheraudio sensor(s), and/or via a direct cable connection, to generatemonitored audio signatures representative of the media being presentedby the media device 205. Additionally or alternatively, the device meter210 may process video signals obtained from the media device 205 via acamera and/or other video sensor(s), and/or a direct cable connection,to generate monitored video signatures (e.g., image signatures)representative of the media being presented by the media device 205. Themonitored signatures generated by the device meter 210 at respectivegeneration intervals can then be compared (e.g., at the examplecrediting facility 120) with known reference signatures toidentify/monitor the media being presented by the media device 205.

In some examples, the site monitor 105 also includes an example peoplemeter 215 to capture audience identification information describing anaudience being exposed to the media presented by the media device 205.In some examples, the people meter 215 can prompt audience member(s) inthe vicinity of the media device 205 to identify which one or more of apossible group of audience members are present in the audience.Additionally or alternatively, in some examples, the people meter 215can automatically identify one or more individuals included in anaudience in the vicinity of the media device 205. In such examples, thedevice meter 210 may combine the metering data (e.g., monitoredsignatures) identifying (e.g., directly or indirectly) the media beingpresented by the media device 205 with the audience identification datadetermined by the people meter 215 to form audience measurement datacharacterizing media exposure (e.g., with demographic information) atthe site being monitored by the example site monitor 105.

The device meter 210 of the illustrated example stores the metering data(or audience measurement data), including the monitored signatures, forreporting to the crediting facility 120 via the reporting medium 125.The monitored signatures reported in the metering data are alsotimestamped to allow the monitored signatures to be associated with theparticular time(s) when the monitored signatures were generated. Thetimestamps also indicate the time(s) at which the monitored mediarepresented by the monitored signatures was presented by the monitoredmedia device 205. The device meter 210 can report the meteringdata/audience measurement data (including the monitored signatures andtimestamps) as it is collected (e.g., streamed), atspecified/predetermined time intervals, when a certain amount of datahas been collected, when an available memory space is filled or reachesa threshold capacity (e.g., 90% or some other percentage being full),and/or via any other periodic, aperiodic and/or event-driven schedule.Example signatures that can be generated and reported by the exampledevice meter 210 of FIG. 2 are illustrated in FIGS. 4A-B, which aredescribed in further detail below.

A block diagram of an example implementation of the referenceidentification system 130 of FIG. 1 is illustrated in FIG. 3. Asdiscussed above, the reference identification system 130 may be locatedseparately from the site monitor(s) 105 and monitors one, some or all ofthe different media being distributed by the media distributor(s) 110via the distribution media 115. In the illustrated example of FIG. 3,the reference identification system 130 includes one or more mediareceivers 305 to receive media being distributed by the mediadistributor(s) 110 via the distribution media 115. For example, themedia receiver(s) 305 can include multiple receivers assigned torespective media distributors 110, such as particular televisionchannels/networks, particular radio channels/networks, particularstreaming services, etc. Additionally or alternatively, one or more ofthe media receiver(s) 305 can be shared (e.g., time-multiplexed) amongmultiple media distributors 110.

The example reference identification system 130 of FIG. 3 also includesone or more signature generators 310 to generate reference signaturesrepresentative of the media received by the media receiver(s) 305. Forexample, the signature generator(s) 310 can include audio signaturegenerator(s) to generate audio signatures representative of the audiosignal(s) corresponding to audio portion(s) of the media received by themedia receiver(s) 305. Additionally or alternatively, the signaturegenerator(s) 310 can include video signature generator(s) to generatevideo (e.g., image) signatures representative of the video signal(s)corresponding to video portion(s) of the media received by the mediareceiver(s) 305. As such, in some examples, the signature generator(s)310 may implement signature generation technique(s) similar to thoseimplemented by the device meter(s) 210 of the example site monitor(s)105.

The signatures generated by the signature generator(s) 310 are referencesignatures that can be used (e.g., by the example crediting facility120) to identify corresponding media being distributed by the mediadistributor(s) 110. For example, for each media distribution receivedand processed by the reference identification system 130, the referencesignatures output from the signature generator(s) are associated withmedia identification data (e.g., such as a source identifier, a streamidentifier, etc.) identifying the particular media represented by thereference signatures. Such media identification data can be known to thereference identification system 130 based on, for example, the knownassociation of the media receiver(s) 305 to the respective mediadistributor(s) 110.

The example reference identification system 130 of FIG. 3 furtherincludes one or more time determiner(s) 315 to determine timeinformation for association with the reference signatures determined bythe signature generator(s) 310. For example, a signature generator 310can trigger a time determiner 315 to determine time information (e.g.,timestamps) indicating when reference signatures for a particular pieceof media (e.g., media segment) were generated and, thus, when thecorresponding reference media was received by the respective mediareceiver 305. The time information can include, for example, theparticular day and/or time-of-day at which a particular referencesignature or block of reference signatures was generated, whichcorresponds to the particular day and/or time-of-day at which the mediarepresented by this reference signature or block of reference signatureswas received by the reference identification system 130. In someexamples, each signature generator 310 is associated with a respectivetime determiner 315. In some examples, groups of signature generators310 are associated with a respective time determiner 315. The timedeterminer(s) 315 can include any timing source, such as a clock, timer,etc., capable of providing time information having an acceptableaccuracy. Example reference signatures that can be generated andreported by the example reference identification system 130 of FIG. 3are illustrated in FIGS. 4A-B, which are described in further detailbelow.

The illustrated example reference identification system 130 alsoincludes an example data reporter 320 to report reference data to thecrediting facility 120 via the example reporting medium 135. Forexample, the reference data reported by the example data reporter 320can include reference signature blocks and associated timestamps andmedia identifiers generated by the signature generator(s) 310 and thetime determiner(s) 315. The data reporter 320 can report the referencedata (including the reference signature blocks, the associatedtimestamps and the media identifiers) as it is collected (e.g.,streamed), at specified/predetermined time intervals, when a certainamount of data has been collected, when an available memory space isfilled or reaches a threshold capacity (e.g., 90% or some otherpercentage being full), etc.

Example media signatures that can be generated and reported by theexample site monitor 105 of FIGS. 1 and/or 2, and/or the examplereference identification system 130 of FIGS. 1 and/or 3 are illustratedin FIGS. 4A-B. The illustrated example of FIG. 4A depicts mediasignatures 405A-C that can be generated (e.g., or otherwise collected)from media at successive signature generation intervals by the sitemonitor 105 and/or the reference identification system 130. The examplemedia signatures 405A-C, collectively referred to as media signatures405, are digital values represented by some number of bits. For example,each media signature 405A-C may be a digital value represented by 3bytes, which corresponds to 24 bits. Of course, the media signatures405A-C may be digital values represented by a different number of bits.As described above, the digital values making up the media signatures405A-C may correspond to, for example, spectral-domain values,time-domain values and/or values of other characteristics generated frommedia signal(s) (e.g., audio signals, video signals, etc.) correspondingto the given media for which the media signatures 405A-C are generated.

In the illustrated example of FIG. 4A, the example media signatures405A-C are associated with respective example timestamps 410A-C,collectively referred to as the timestamps 410. For example, thetimestamps 410A-C can be day/time values indicating the times at whichthe respective media signatures 405A-C were generated. For example, thesite monitor 105 and/or the reference identification system 130 may beconfigured to generate site signatures at a particular signaturegeneration interval (e.g., approximately a 16 ms. interval, or at someother interval). In such examples, the timestamps 410A-C can havesufficient resolution to identify the particular signature generationinterval at which a particular one of the media signatures 405A-C wasgenerated. Furthermore, when the media signatures 405A-C correspond tomedia signatures generated by the reference identification system 130,the timestamps 410A-C indicate the original times at which the mediacorresponding to the media signatures 405A-C was provided (e.g.,distributed, broadcast, etc.) by the respective media distributor 110.However, when the media signatures 405A-C correspond to media signaturesgenerated by the site monitor 105, the timestamps 410A-C indicate thetimes at which the media corresponding to the media signatures 405A-Cwas presented by the monitored media device 205 (which may be the sameor different from the original times at which the media was distributedby the respective media distributor 110 depending on, for example,whether the media undergoes time-shifting prior to being presented bythe monitored media device 205).

Although each media signature 405A-C is associated with a respectivetimestamp 410A-C in the example of FIG. 4A, in other examples, such asin the example of FIG. 4B, multiple media signatures (e.g., a packet ofmedia signatures, also referred to as a signature packet) may beassociated with a single timestamp (e.g., which identifies the startingtime at which the packet of media signatures was generated). Theillustrated example of FIG. 4B depicts media signatures 455 that can begenerated (e.g., or otherwise collected) from media at successivesignature generation intervals by the site monitor 105 and/or thereference identification system 130. Like the example media signatures405A-C, the example media signatures 455 are digital values representedby some number of bits. For example, each one of the media signatures455 may be a digital value represented by 3 bytes, which corresponds to24 bits. Of course, the media signatures 455 may be digital valuesrepresented by a different number of bits. As described above, thedigital values making up the media signatures 455 may correspond to, forexample, spectral-domain values, time-domain values and/or values ofother characteristics generated from media signal(s) (e.g., audiosignals, video signals, etc.) corresponding to the given media for whichthe media signatures 455 are generated.

In the illustrated example of FIG. 4B, the packet of media signatures455 is associated collectively with an example timestamp 460. Forexample, the timestamp 460 can be a day/time value indicating the timeat which the starting media signature (or some other media signature) inthe packet of media signatures 455 was generated. In some examples, thetimestamp 460 is structured to have sufficient resolution to identifythe start time at which successive media signature packets weregenerated. For example, if the packet of media signatures 455 includessixty-four (64) media signatures each generated at 16 ms. intervals,then the timestamp 460 may have a resolution of at least 1 second (or afraction of a second) to permit accurate representation of the differenttimes associated with different media signature packets.

In some examples, the site monitor(s) 105 may generate media signaturesand timestamps in accordance with the example of FIG. 4A, whereas thereference identification system 130 may generate media signatures andtimestamps in accordance with the example of FIG. 4B, or vice versa. Insome examples, the example media signatures 405A-C and/or 455 aregenerated by the example site monitor(s) 105 and/or the examplereference identification system 130 based on a spectral analysis of theaudio stream of given media as follows. A block of audio consisting of4096 samples is analyzed through use of a Discrete Fourier Transform.The resulting spectral frequency components, which include of real andimaginary parts, are convolved with a pair of complex functions togenerate a pair of modified spectra F₁(u) and F₂(u), where 0≤u<4096 isthe frequency index. The frequency index range is divided into 24 bandsconsisting of 32 consecutive indices starting at index 127. The energyassociated with each band of frequencies in F₁(u) is compared with acorresponding band in F₂(u) to set a bit of the signature as a 1 or 0.With 24 such bands, a 24-bit signature that characterizes the block of4096 samples can be computed. A sequence of such signatures is generatedby sliding a window of length 4096 samples in increments of 128 samplesto generate successive 24-bit integer signature. Thus, each 24-bitdigital signature/fingerprint characterizing the audio is separated intime by 16 ms. (128 samples) from its neighbors in the sequence.

A block diagram of a first example implementation of the creditingfacility 120 of FIG. 1 is illustrated in FIG. 5. The block diagram ofFIG. 5 illustrates structures associated with implementing signaturematching at the crediting facility 120. Other structures implemented bythe crediting facility 120 have been omitted for clarity.

Turning to FIG. 5, the illustrated example crediting facility 120includes an example reference interface 505 to interface with areference identification system, such as the example referenceidentification system 130 of FIGS. 1 and/or 3. As such, the referenceinterface 505 can be implemented using any interface technology,communication device(s), etc., capable of interfacing with and receivingdata via the example reporting medium 135. The example referenceinterface 505 receives reference data from the reference identificationsystem 130, including reference signatures and associated timestampsrepresentative of different reference media sources received by thereference identification system 130 (e.g., corresponding to thedifferent media distributor(s) 110).

The example crediting facility 120 of FIG. 5 also includes an examplereference signature storage 510 to store the respective sequences ofreference signatures and associated reference timestamps received viathe reference interface 505 for different reference media sources. Theexample reference signature storage 510 may be implemented by anynumber(s) and/or type(s) of volatile and/or non-volatile memory,storage, etc., or combination(s) thereof, such as the example volatilememory 1314 and/or the example mass storage device(s) 1328 included inthe example processing system 1300 of FIG. 13, which is described infurther detail below.

The example crediting facility 120 of FIG. 5 further includes an examplemonitor interface 515 to interface with one or more site monitors, suchas the example site monitor(s) 105 of FIGS. 1 and/or 2. As such, themonitor interface 515 can be implemented using any interface technology,communication device(s), etc., capable of interfacing with and receivingdata via the example reporting medium 125. The example monitor interface515 receives metering data from the site monitor(s) 105, includingmonitored signatures and associated timestamps representative of mediapresented by media device(s) monitored by the site monitor(s) 105.

The example crediting facility 120 of FIG. 5 also includes an examplemonitored signature storage 520 to store the respective sequences ofmonitored signatures and associated reference timestamps received viathe monitor interface 515 from ones of the site monitor(s). The examplemonitored signature storage 520 may be implemented by any number(s)and/or type(s) of volatile and/or non-volatile memory, storage, etc., orcombination(s) thereof, such as the example volatile memory 1314 and/orthe example mass storage device(s) 1328 included in the exampleprocessing system 1300 of FIG. 13, which is described in further detailbelow. In some examples, the monitored signature storage 520 and thereference signature storage 510 may be implemented by separate storageelements, whereas in other examples, the monitored signature storage 520and the reference signature storage 510 may be implemented by the samestorage element.

In the illustrated example of FIG. 5, the example crediting facility 120includes two example media signature comparators 525 and 530 to performsignature matching for media monitoring. The example signaturecomparators 525 and 530 perform respective media signature matchingprocedures to compare a sequence of monitored signatures from themonitored signature storage 520 with different sequences of referencesignatures from the reference signature storage 510, which arerepresentative of different possible reference media sources. Forexample, such signature matching procedures may evaluate one or morecomparison criteria, such as a cross-correlation value, a Hammingdistance, population (POP) count, etc., to determine whether a group, orneighborhood, of monitored signatures matches a particular group, orneighborhood, of reference signatures representative of a particularreference media source. In the illustrated example of FIG. 5, the firstexample signature comparator 525 is configured to perform such a mediasignature matching procedure using a first example analysis window 535,and the second example signature comparator 530 is configured to performa same or different media signature matching procedure using a secondexample analysis window 540. In the illustrated example, the secondexample analysis window 540 is larger than the first example analysiswindow 535. Furthermore, in the illustrated example of FIG. 5, the twoexample signature comparators 525 and 530 operate in parallel to producerespective signature matching results associated with the differentanalysis windows 535 and 540.

The different analysis windows 535 and 540 define the sizes of thegroups, or neighborhoods, of monitored and reference media signaturesthat are compared by the respective signature comparators 525 and 530 todetermine whether monitored media represented by the monitored mediasignatures matches the particular reference media source represented bya given group of reference media signatures. For example, consider anexample television program having a duration of sixty (60) minutes. Torepresent this television program with media signatures (e.g., audiosignatures) generated at 16 ms intervals in accordance with the examplesdescribed, the reference identification system 130 would generate asequence of 225,000 reference signatures, with each signature being a24-bit integer, which would be stored in the reference signature storage510. An example site monitor 105 monitoring a media device presentingthis same television program as provided by one of the mediadistributors 110 would generate a similar sequence of 24-bit monitoredaudio signatures, which would be stored in the monitored signaturestorage 520. In general, the sequence of monitored media signaturesgenerated by the site monitor 105 will differ from the sequence ofreference signatures generated by the reference identification system130 for this same television program because, for example, the signaturegeneration intervals for the two different sequences may not betime-aligned, the media signal (e.g., audio signal) processed by thesite monitor 105 may be sensed non-invasively (e.g., with a microphone)and, thus, may be subjected to more ambient noise than the media signal(e.g., audio signal) processed by the reference identification system130, etc. Nevertheless, the signature comparison algorithm(s)implemented by the signature comparators 525 and 530 will likely be ableto detect one or more of the monitored signatures that match arespective one or more of the reference signatures for this televisionprogram.

In the illustrated example of FIG. 5, when the example signaturecomparator 525 finds such a match, the signature comparator 525 furtherexamines a neighborhood of monitored and reference signaturessurrounding the match location (e.g., the time associated with thematching signatures) to determine an overall signature matching resultbetween the monitored and reference signatures sequences for that matchlocation. In the illustrated example of FIG. 5, the first analysiswindow 535 defines the size of the neighborhoods of monitored andreference signatures to be compared by the signature comparator 525 todetermine whether the monitored media matches a particular referencemedia source. In some examples, the first analysis window 535 is aspecified to be a four (4) second analysis window, which causes thesignature comparator 525 to process neighborhoods of monitored andreference signatures including 256 signatures, respectively (e.g.,because 256 signatures spaced at 16 ms. intervals cover a time span on256×0.016=4.096 seconds). However, in some examples, because consecutivemedia signatures may not exhibit substantial bit changes, the signaturecomparator 525 may reduce its processing load by choosing every 8^(th)(or some other number) media signature in the respective monitored andreference signature sequences to construct neighborhoods of 32signatures for comparison. The spacing between each of these 32signatures is 8×16=128 ms, and the total time span of the 32 signaturesis again approximately 4 seconds, corresponding to the first analysiswindow 535.

In some examples, the signature matching procedure implemented by thesignature comparator 525 includes calculating a Hamming distance betweenthe 24×32=768 bits constituting the 32 signatures in the reference andmonitored signature neighborhoods defined by the first analysis window535, which is specified to be 4 seconds in the foregoing example. Insome such examples, the signature comparator 525 employs a comparisonthreshold to improve the reliability of the outputted match results. Forexample, in the preceding example, the signature comparator 525 mayutilize a threshold of 200, which specifies that, for the signaturecomparator 525 to determine that the neighborhood of monitoredsignatures matches the neighborhood of reference signatures, the Hammingdistance between the two neighborhoods must be less than (or less thanor equal to) 200, which means that no more than 200 of the 768 bits candiffer between the two neighborhoods. Of course, other threshold valuescould be used.

As noted above, a technical problem faced by prior media monitoringsystems employing media signatures is the signature matching uncertaintyresulting from (1) multiple potential reference media sources havingreference signatures capable of matching a given group of monitoredmedia signatures and/or (2) the same reference media source havingmultiple different groupings of reference signatures capable of matchingthe given group of monitored media signatures. For example, suchmatching uncertainty can occur when multiple instances of the same media(e.g., the same television program, the same commercial, etc.) arebroadcast at different times and/or on different television channels. Insome examples of television audience measurement, program viewing iscredited for up to eight (8) days after the original air date. If amonitored site (e.g., corresponding to a panelist) household has accessto, for example, 100 channels, represented as CH1, CH2, . . . , CH100, areference media signature database covering an 8 day period for all the100 channels may be maintained in the example reference signaturestorage 510. Consider an example in which, in the particular marketwhere this household is located, a national 30-second commercial spot,referred to as AD1, is contracted to air on channels CH4, CH5 and CH7,and at multiple times during the day. Further, assume a television setor other media device at this monitored site was tuned to a channel, sayCH4, at 8:08 p.m., and the commercial spot AD1 was received. Prior mediamonitoring system employing signature matching using an analysis windowof 4 seconds may yield multiple successful matches corresponding to theairing of this commercial spot on CH4, CH5, and CH7 and at multiple timeinstants on different days. This is because, within the 4 second window,the reference media signatures for these different airings will besubstantially the same. Similar behavior may also be observed with thesignature comparator 525 when it is configured with the first analysiswindow 535 having a value of 4 seconds.

For example, the signature comparator 525 may implement a signaturematching procedure that determines that the reference media signatureneighborhood yielding the smallest Hamming distance is the match to agiven monitored media sequence neighborhood. The 4 second neighborhoodspecified by the first analysis window 535 may result in multipledifferent possible reference sources of AD1 (e.g., corresponding to thedifferent channels CH4, CH5 and CH7, and at multiple times during theday) having the same, or similar, sequences of reference signatureswithin this neighborhood. Furthermore, due to noise, degradation, etc.,associated with the microphone captured audio from which the monitoredsignatures are derived, the signature comparator 525 might report thereference source corresponding to AD1 being broadcast on CH5 at 7:21p.m. as having the lowest Hamming distance. This would be incorrect inthis example because the monitored media device presented the instanceof AD1 broadcast on CH4, at 8:08 p.m. Accurate crediting of the viewingusing the signature comparator 525 configured with the first analysiswindow 535 having a value of 4 seconds becomes difficult in this examplebecause the signature comparator 525 used the 4 second analysis windowdescribed above to compute the Hamming distance, which yielded multiplepotential matching reference neighborhoods.

The example crediting facility 120 of FIG. 5 includes the second examplesignature comparator 530 configured by the second example analysiswindow 540 to resolve, or at least reduce, such signature matchinguncertainty resulting from (1) multiple potential reference mediasources having reference signatures capable of matching a given group ofmonitored media signatures and/or (2) the same reference media sourcehaving multiple different groupings of reference signatures capable ofmatching the given group of monitored media signatures. As describedabove, the second example signature comparator 530 is configured toperform a signature matching procedure, which may be the same ordifferent from the signature matching procedure performed by the firstexample signature comparator 525, but using the second example analysiswindow 540, which is larger than the first example analysis window 535.

For example, the second example analysis window 540 may be specified tobe thirty-two (32) seconds, or some other value, that is larger than themedia segments of interest, such as 30 second commercials in thepreceding example. Such a larger second example analysis window 540spans multiple media segments of interest (e.g., such as multiplecommercials broadcast on a given channel, or a commercial and atelevision program broadcast on a given channel, etc.). The particularcombination of successive media segments available to a monitored mediadevice from a given reference media source on a given day and at a giventime-of-day is likely to be unique (e.g., such as when the differentpossible reference media sources correspond to different possibletelevision channels). Accordingly, the larger neighborhood of mediasignatures defined by the second example analysis window 540 is alsolikely to be unique to a given reference media source. Thus, the secondexample signature comparator 530, which performs its signature matchingprocedure using the second example analysis window 540, is able toresolve or reduce the foregoing signature matching uncertainty becausethe larger neighborhoods of monitored and reference signatures definedby the second example analysis window 540 represent combinations ofsuccessive media segments that are likely to be unique to a givenpossible reference media source.

In some examples, the second example signature comparator 530 also usesa comparison threshold to improve the reliability of the outputted matchresults. However, the comparison threshold used by the second examplesignature comparator 530 may be larger than the comparison thresholdused by the first example signature comparator 525 due to the largeranalysis window configured for the signature comparator 530. Forexample, if the signature matching procedure implemented by thesignature comparator 530 includes calculating a Hamming distance, theHamming distance will be between the 24×256=6144 bits constituting the256 signatures in the reference and monitored signature neighborhoodsdefined by the second analysis window 540, which is specified to be 32seconds in the foregoing example. (Taking every 8 signature ofsignatures spaced 16 ms apart over a 32 second window yields 256signatures.) In some such examples, the signature comparator 530 mayutilize a threshold of 1600, which specifies that, for the signaturecomparator 530 to determine that the neighborhood of monitoredsignatures matches the neighborhood of reference signatures, the Hammingdistance between the two neighborhoods must be less than (or less thanor equal to) 1600, which means that no more than 1600 of the 6144 bitscan differ between the two neighborhoods. Of course, other thresholdvalues could be used.

FIG. 6 illustrates an example version of the second example analysiswindow 540. As depicted in the example of FIG. 6, the second exampleanalysis window 540 is specified to be large enough to encompass, ingeneral, a combination of an example commercial segment 605 and aportion of an example program content segment 610, or a combination oftwo successive example commercial segments 615 and 620. Thesecombinations of successive media segments will likely be unique to theparticular reference media source (e.g., particular media distributor110) providing the illustrated sequence of media segments 605-620.Accordingly, the resulting sequences of monitored and reference mediasignatures representing this particular sequence of media segments605-620 are also likely to be unique, thereby reducing, or resolving,the signature matching uncertainty that can arise when each such mediasegment is analyzed in isolation.

First example signature matching results 700 output from the firstexample signature comparator 525 using the first example analysis window535 set to 4 seconds is illustrated in FIG. 7. Second example signaturematching results 800 output from the second example signature comparator530 using the second example analysis window 540 set to 32 seconds isillustrated in FIG. 8. The example signature matching resultsillustrated in FIGS. 7 and 8 further demonstrate the potential benefitsof using the larger analysis window 540 for signature matching. In theillustrated examples of FIGS. 7 and 8, each row of signature matchingresults 700 and 800 represent the signature matching results returned bythe respective signature comparators 525 and 530 for successivemonitored signature packets retrieved from the monitored signaturestorage 520. In the illustrated examples, each monitored signaturepacket (labeled as QPKT) has a numeric identifier and corresponds to asequence of signatures representing a media duration of approximately 2seconds. As such, the example signature matching results 700 and 800have a time resolution of approximately 2 seconds, with each matchingresult identifying the particular reference source determined to matchthe corresponding monitored signature packet. In the example matchingresults 700 and 800, the matching reference source is identified by asource identifier (SID) and a reference timestamp (TS) corresponding tothe time when the matching reference media was received by the referenceidentification system 130. The example matching results 700 and 800 alsolist the Hamming distance (HAM) between the monitored signatures and thereference signatures for the reference source identified as the bestmatch, and a GAP indicator to indicate the gap with respect to theprevious successful match.

The example matching results 700 of FIG. 7 illustrate the signaturematching uncertainty problem associated with the smaller 4 secondanalysis window 535. Because each of the monitored signature packetsincludes signatures covering a 2-second interval, the 4 second analysiswindow 535 causes two (2) adjacent monitored signature packets to beincluded in the neighborhood of monitored signatures used to generateeach one of the example matching results 700 corresponding to arespective one of the input monitored signature packets. In theillustrated example of FIG. 7, the actual reference media sourcecorresponding to the monitored media signatures was a television channelcorresponding to SID 4000. However, because the matching results 700 aredetermined with the smaller 4 second analysis window 535, some of theneighborhoods of monitored signature packets instead matched broadcastsof the same media on television channels corresponding to SIDs 3000 and5000 (see e.g., the example results 700 for QPKTs 930-944 and 947-948),but at different times as indicated by the discontinuities in thesequence of reference timestamps for the example results identifyingSIDs 3000 and 5000. Such reference timestamp discontinuities can be anindication of signature matching uncertainty, as discussed in furtherdetail below. Furthermore, the example matching results 700 includeinstances in which no match satisfying the matching threshold was found(see e.g. the example results 700 for QPKTs 914-915).

In contrast, the example matching results 800 of FIG. 8 illustrate theability of the larger 32 second analysis 540 to resolve the signaturematching uncertainty associated with the smaller 4 second analysiswindow 535. Because each of the monitored signature packets includessignatures covering a 2-second interval, the 32 second analysis window540 causes sixteen (16) adjacent monitored signature packets to beincluded in the neighborhood of monitored signatures used to generateeach one of the example matching results 700 corresponding to arespective one of the input monitored signature packets. In theillustrated example of FIG. 8, the actual reference media sourcecorresponding to the monitored media signatures was also the televisionchannel corresponding to SID 4000. Because the matching results 800 aredetermined with the larger 32 second analysis window 540, the matchingresults were not susceptible to instances where brief media segmentswere available from multiple different reference sources (e.g., SIDs thetelevision channels corresponding to SIDs 3000 and 5000). Instead, withthe larger 32 second analysis window 540), the matching results 800consistently identify SID 4000 as the source of the monitored media, andthe matching reference timestamps consistently increment at the propertime resolution of approximately 2 seconds. Also, as expected, theHamming distance values for the example matching results 800 are largerthan the Hamming distance values for the example matching results 700due to the matching results 800 being determined for largerneighborhoods of signatures (e.g., by approximately a factor of 8 due tothe second analysis window 540 being 8 times larger than the firstanalysis window 535).

Returning to FIG. 5, in the illustrated example, the example signaturecomparators 525 and 530 included in the example crediting facility 120operate in parallel to determine their respective signature matchingresults based on the different respective analysis windows 535 and 540.In the illustrated example of FIG. 5, the example crediting facility 120further includes an example matching results selector 545 to selectwhether the example crediting facility 120 is to output the firstsignature matching results from the first example signature comparator525 or the second signature matching results from the second examplesignature comparator 530. In some examples, the matching resultsselector 545 evaluates the first signature matching results output fromthe first example signature comparator 525 to determine whether thosefirst signature matching results are indicative of a matchinguncertainty condition. In some such examples, the matching resultsselector 545 selects to output the second signature matching resultsfrom the second example signature comparator 530 in response todetermining the first signature matching results are indicative of amatching uncertainty condition. However, in some such examples, thematching results selector 545 selects to output the first signaturematching results from the first example signature comparator 525 insteadin response to determining the first signature matching results are notindicative of a matching uncertainty condition.

Such an example matching results selector 545 allows the examplecrediting facility 120 of FIG. 5 to use a long analysis window when asignature matching uncertainty conditions is detected, which can helpresolve such uncertainties, thereby allowing the unique reference mediasource corresponding to the monitored media to be accurately identified.However, when signature matching uncertainty conditions are notdetected, disclosed example media monitoring systems can switch toutilizing a short analysis window, which supports finer signaturematching granularity, thereby enabling channel surfing and similar mediaconsumption behaviors to be accurately monitored.

In some examples, the matching results selector 545 determines whetherthe first signature matching results output from the first examplesignature comparator 525 are indicative of a matching uncertaintycondition by examining the matching results over an observation periodto detect inconsistencies in the results. For example, for typical mediaexposure scenarios, one would expect the media signature matchingresults over a moderate observation period of, say, one or a few minutesto correspond to the same reference media source (or just a fewreference media sources), and with reference timestamps that incrementcontinuously over the observation period by amounts within a range basedon a time resolution associated with the matching results (e.g., such aswithin a range of 1 to 3 seconds for a time resolution of 2 secondsexhibited by the example results 700 and 800 of FIGS. 7 and 8). Thus, insome examples, the matching results selector 545 may determine whethersuccessive matching results from the first example signature comparator525, which uses the shorter (e.g., 4 second) analysis window 535, areassociated with different (e.g., changing) reference media sourcesand/or discontinuous timestamps within a given observation time period,which indicates the shorter window 535 is causing the first examplesignature comparator 525 to oscillate among multiple potential matchingreference sources. For example, the matching results selector 545 maydetermine the matching reference timestamps are discontinuous in theobservation period when, over the observation period, successive ones ofthe reference timestamps do not increment relative to preceding ones ofthe reference timestamps by a first amount within a range (e.g., 1 to 3seconds) based on a time resolution (e.g., 2 seconds) associated withthe matching results output by the first example signature comparator525. If such behavior is detected, the matching results selector 545selectively switches to outputting the matching results from the secondexample signature comparator 530, which uses the longer (e.g., 32second) analysis window 540.

Additionally or alternatively, in some examples, the matching resultsselector 545 examines the matching results from the first examplesignature comparator 525, which uses the shorter (e.g., 4 second)analysis window 535, to determine whether, for a given signaturematching result (e.g., corresponding to a given monitored signaturepacket), multiple possible reference sources yield respectiveintermediate matching results satisfying a comparison threshold (e.g.,have associated Hamming distances that are less than or equal to athreshold value). Such behavior is also indicative of the shorteranalysis window 535 causing the first example signature comparator 525to oscillate among multiple potential matching reference sources.Accordingly, if such behavior is detected, the matching results selector545 selectively switches to outputting the matching results from thesecond example signature comparator 530, which uses the longer (e.g., 32second) analysis window 540.

In some examples, the matching results selector 545 continues to causethe example crediting facility 120 of FIG. 5 to output the matchingresults from the second example signature comparator 530, which uses thelonger (e.g., 32 second) analysis window 540, until the matching resultsfrom the first example signature comparator 525, which uses the shorter(e.g., 4 second) analysis window 535, no longer exhibit the foregoingbehavior indicative of signature matching uncertainty. When that occurs,the matching results selector 545 selectively switches to outputting thematching results from the first example signature comparator 525, whichuses the shorter (e.g., 4 second) analysis window 535.

A block diagram of a second example implementation of the creditingfacility 120 of FIG. 1 is illustrated in FIG. 9. The block diagram ofFIG. 9 illustrates structures associated with implementing signaturematching at the crediting facility 120. Other structures implemented bythe crediting facility 120 have been omitted for clarity. Furthermore,the second example implementation of the crediting facility 120 of FIG.9 includes many elements in common with the first example implementationillustrated in FIG. 5. Such like elements include the example referenceinterface 505, the example reference signature storage 510, the examplemonitor interface 515, the example monitored signature storage 520, thefirst example analysis window 535, and the second example analysiswindow 540, which are labeled with the same reference numerals in FIGS.5 and 9. The detailed descriptions of these like elements are providedabove in connection with the discussion of FIG. 5 and, in the interestof brevity, are not repeated in the discussion of FIG. 9.

However, unlike the first example implementation of the creditingfacility 120 is illustrated in FIG. 5, which includes two examplesignature comparators 525 and 530 operating in parallel, the secondexample implementation of the crediting facility 120 illustrated in FIG.9 includes one example media signature comparator 925, which can beselectively configured with either of the two example analysis windows535 and 540. Like the example signature comparators 525 and 530, theexample signature comparator 925 performs a signature matching procedureto compare a sequence of monitored signatures from the monitoredsignature storage 520 with different sequences of reference signaturesfrom the reference signature storage 510, which are representative ofdifferent possible reference media sources. For example, such asignature matching procedure may evaluate one or more comparisoncriteria, such as a cross-correlation value, a Hamming distance,population (POP) count, etc., to determine whether a group, orneighborhood, of monitored signatures matches a particular group, orneighborhood, of reference signatures representative of a particularreference media source.

Furthermore, the second example implementation of the crediting facility120 illustrated in FIG. 9 includes an example matching results selector945 to select whether to configure the example signature comparator 925to perform its signature matching procedure using the first (e.g.,short) analysis window 535 or the second (e.g., long) analysis window540. For example, the matching results selector 945 may initiallyconfigure the example signature comparator 925 to use the first (e.g.,short) analysis window 535, and then evaluate the matching resultsoutput by the signature comparator 925 to determine, as described abovefor the matching results selector 545, whether the results areindicative of a matching uncertainty condition. If the matching resultsare indicative of a matching uncertainty condition, the example matchingresults selector 945 configures the example signature comparator 925 touse the second (e.g., long) analysis window 540. In some examples, afterconfiguring the signature comparator 925 to use the second (e.g., long)analysis window 540, the matching results selector 945 periodically oraperiodically (e.g., according to some testing schedule) configures theexample signature comparator 925 to use the first (e.g., short) analysiswindow 535 to determine whether the first window no longer exhibits thematching uncertainty condition(s). If the matching uncertaintycondition(s) are no longer detected, the matching results selector 945continues to cause the example signature comparator 925 to use the first(e.g., short) analysis window 535. However, if the matching uncertaintycondition(s) are detected, the matching results selector 945 switchesback to configuring the signature comparator 925 to use the second(e.g., long) analysis window 540. Such an implementation avoids theadditional processing costs associated with operating multiple signaturecomparators in parallel, but adds potential latency to switching betweenusing the first (e.g., short) analysis window 535 vs. the second (e.g.,long) analysis window 540 to perform signature matching.

While example manners of implementing the example media monitoringsystem 100 are illustrated in FIGS. 1-9, one or more of the elements,processes and/or devices illustrated in FIGS. 1-9 may be combined,divided, re-arranged, omitted, eliminated and/or implemented in anyother way. Further, the example site monitor(s) 105, the exampledistribution media 115, the example crediting facility 120, the examplereporting medium 125, the example reference identification system 130,the example reporting medium 135, the example device meter 210, theexample people meter 215, the example media receiver(s) 305, the examplesignature generators 310, the example time determiner(s) 315, theexample data reporter 320, the example reference interface 505, theexample reference signature storage 510, the example monitor interface515, the example monitored signature storage 520, the first examplesignature comparator 525, the second example signature comparator 530,the first example analysis window 535, the second example analysiswindow 540, the example matching results selector 545, the examplesignature comparator 925, the example matching results selector 945and/or, more generally, the example media monitoring system 100 of FIGS.1-9 may be implemented by hardware, software, firmware and/or anycombination of hardware, software and/or firmware. Thus, for example,any of the example site monitor(s) 105, the example distribution media115, the example crediting facility 120, the example reporting medium125, the example reference identification system 130, the examplereporting medium 135, the example device meter 210, the example peoplemeter 215, the example media receiver(s) 305, the example signaturegenerators 310, the example time determiner(s) 315, the example datareporter 320, the example reference interface 505, the example referencesignature storage 510, the example monitor interface 515, the examplemonitored signature storage 520, the first example signature comparator525, the second example signature comparator 530, the first exampleanalysis window 535, the second example analysis window 540, the examplematching results selector 545, the example signature comparator 925, theexample matching results selector 945 and/or, more generally, theexample media monitoring system 100 could be implemented by one or moreanalog or digital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)).When reading any of the apparatus or system claims of this patent tocover a purely software and/or firmware implementation, at least one ofthe example media monitoring system 100, the example site monitor(s)105, the example distribution media 115, the example crediting facility120, the example reporting medium 125, the example referenceidentification system 130, the example reporting medium 135, the exampledevice meter 210, the example people meter 215, the example mediareceiver(s) 305, the example signature generators 310, the example timedeterminer(s) 315, the example data reporter 320, the example referenceinterface 505, the example reference signature storage 510, the examplemonitor interface 515, the example monitored signature storage 520, thefirst example signature comparator 525, the second example signaturecomparator 530, the first example analysis window 535, the secondexample analysis window 540, the example matching results selector 545,the example signature comparator 925 and/or the example matching resultsselector 945 is/are hereby expressly defined to include a tangiblecomputer readable storage device or storage disk such as a memory, adigital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc.storing the software and/or firmware. Further still, the example mediamonitoring system 100 may include one or more elements, processes and/ordevices in addition to, or instead of, those illustrated in FIGS. 1-9,and/or may include more than one of any or all of the illustratedelements, processes and devices.

Flowcharts representative of example machine readable instructions forimplementing the example media monitoring system 100, the example sitemonitor(s) 105, the example distribution media 115, the examplecrediting facility 120, the example reporting medium 125, the examplereference identification system 130, the example reporting medium 135,the example device meter 210, the example people meter 215, the examplemedia receiver(s) 305, the example signature generators 310, the exampletime determiner(s) 315, the example data reporter 320, the examplereference interface 505, the example reference signature storage 510,the example monitor interface 515, the example monitored signaturestorage 520, the first example signature comparator 525, the secondexample signature comparator 530, the first example analysis window 535,the second example analysis window 540, the example matching resultsselector 545, the example signature comparator 925 and/or the examplematching results selector 945 are shown in FIGS. 10-12. In theseexamples, the machine readable instructions comprise one or moreprograms for execution by a processor, such as the processors 1312and/or 1412 shown in the example processor platform 1300 and 1400discussed below in connection with FIGS. 13 and 14. The one or moreprograms, or portion(s) thereof, may be embodied in software stored on atangible computer readable storage medium such as a CD-ROM, a floppydisk, a hard drive, a digital versatile disk (DVD), a Blu-ray Disk™, ora memory associated with the processors 1312 and/or 1412, but the entireprogram or programs and/or portions thereof could alternatively beexecuted by a device other than the processors 1312 and/or 1412, and/orembodied in firmware or dedicated hardware (e.g., implemented by anASIC, a PLD, an FPLD, discrete logic, etc.). Further, although theexample program(s) is(are) described with reference to the flowchartsillustrated in FIGS. 10-12, many other methods of implementing theexample media monitoring system 100, the example site monitor(s) 105,the example distribution media 115, the example crediting facility 120,the example reporting medium 125, the example reference identificationsystem 130, the example reporting medium 135, the example device meter210, the example people meter 215, the example media receiver(s) 305,the example signature generators 310, the example time determiner(s)315, the example data reporter 320, the example reference interface 505,the example reference signature storage 510, the example monitorinterface 515, the example monitored signature storage 520, the firstexample signature comparator 525, the second example signaturecomparator 530, the first example analysis window 535, the secondexample analysis window 540, the example matching results selector 545,the example signature comparator 925 and/or the example matching resultsselector 945 may alternatively be used. For example, with reference tothe flowcharts illustrated in FIGS. 10-12, the order of execution of theblocks may be changed, and/or some of the blocks described may bechanged, eliminated, combined and/or subdivided into multiple blocks.

As mentioned above, the example processes of FIGS. 10-12 may beimplemented using coded instructions (e.g., computer and/or machinereadable instructions) stored on a tangible computer readable storagemedium such as a hard disk drive, a flash memory, a read-only memory(ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, arandom-access memory (RAM) and/or any other storage device or storagedisk in which information is stored for any duration (e.g., for extendedtime periods, permanently, for brief instances, for temporarilybuffering, and/or for caching of the information). As used herein, theterm tangible computer readable storage medium is expressly defined toinclude any type of computer readable storage device and/or storage diskand to exclude propagating signals and to exclude transmission media. Asused herein, “tangible computer readable storage medium” and “tangiblemachine readable storage medium” are used interchangeably. Additionallyor alternatively, the example processes of FIGS. 10-12 may beimplemented using coded instructions (e.g., computer and/or machinereadable instructions) stored on a non-transitory computer and/ormachine readable medium such as a hard disk drive, a flash memory, aROM, a CD, a DVD, a cache, a RAM and/or any other storage device orstorage disk in which information is stored for any duration (e.g., forextended time periods, permanently, for brief instances, for temporarilybuffering, and/or for caching of the information). As used herein, theterm non-transitory computer readable medium is expressly defined toinclude any type of computer readable storage device and/or storage diskand to exclude propagating signals and to exclude transmission media. Asused herein, when the phrase “at least” is used as the transition termin a preamble of a claim, it is open-ended in the same manner as theterms “comprising” and “including” are open ended. Also, as used herein,the terms “computer readable” and “machine readable” are consideredequivalent unless indicated otherwise.

An example program 1000 that may be executed to implement the examplecrediting facility 120 of FIGS. 1 and/or 5 is represented by theflowchart shown in FIG. 10. For convenience, and without loss ofgenerality, execution of the example program 1000 is described from theperspective of the example crediting facility 120 of FIG. 5 operating inthe example media monitoring system 100 of FIG. 1. With reference to thepreceding figures and associated written descriptions, the exampleprogram 1000 of FIG. 10 begins execution at block 1005 at which thefirst and second example signature comparators 525 and 530 of thecrediting facility 120 access, from the example monitored signaturestorage 520, a sequence of monitored media signatures to be processed.At block 1010, the first and second signature comparators 525 and 530access, from the example reference signature storage 510, sequences ofreference media signatures to be compared with the sequence of monitoredmedia signatures accessed at block 1005. As described above, thesequences of reference media signatures accessed at block 1010 arerepresentative of respective different reference media sources, one ofwhich the crediting facility 120 will attempt to identify as the sourceof the monitored media represented by the sequence of monitored mediasignatures.

At block 1015, the first signature comparator 525 performs, as describedabove, a signature matching procedure configured with the first (e.g.,short) example analysis window 535 on the sequence of monitored mediasignatures accessed at block 1005 to compare those monitored signatureswith the respective sequences of reference media signatures accessed atblock 1010. As described above, the first (e.g., short) analysis window535 defines the sizes (e.g., in time, in number of signatures, etc.) ofthe neighborhood of the sequence of monitored media signatures to becompared by the first signature comparator 525 with neighborhoods of therespective ones of the reference media sequences to determine respectivesignature matching results corresponding to each comparison instant oftime (e.g., corresponding to the time resolution of the matchingresults, such a matching result being determined for each monitoredsignature packet, as described above). In parallel, at block 1020, thesecond signature comparator 530 performs, as described above, asignature matching procedure configured with the second (e.g., long)example analysis window 540 on the sequence of monitored mediasignatures accessed at block 1005 to compare those monitored signatureswith the respective sequences of reference media signatures accessed atblock 1010. As described above, the second (e.g., long) analysis window540 defines the sizes (e.g., in time, in number of signatures, etc.) ofthe neighborhood of the sequence of monitored media signatures to becompared by the second signature comparator 530 with neighborhoods ofthe respective ones of the reference media sequences to determinerespective signature matching results corresponding to each comparisoninstant of time (e.g., corresponding to the time resolution of thematching results, such a matching result being determined for eachmonitored signature packet, as described above).

At block 1200, the example matching results selector 545 of thecrediting facility determines, as described above, whether the firstmatching results output by the first signature comparator 525 at block1015, which correspond to performing the signature matching procedurewith the first (e.g., short) analysis window 535, are indicative of amatching uncertainty condition. Example machine readable instructionscapable of implementing the processing at block 1200 are illustrated inFIG. 12, which is described in further detail below. If the matchingresults selector 545 does not detect a matching uncertainty conditionwhen evaluating the first matching results corresponding to the first(e.g., short) analysis window 535 (block 1030), processing proceeds toblock 1035 at which the matching results selector 545 selects to causethe crediting facility 120 to output the first matching resultsdetermined at block 1015 by the first signature comparator 525performing the signature matching procedure with the first (e.g., short)analysis window 535. However, if the matching results selector 545 doesdetect a matching uncertainty condition when evaluating the firstmatching results corresponding to the first (e.g., short) analysiswindow 535 (block 1030), processing proceeds to block 1040 at which thematching results selector 545 selects to cause the crediting facility120 to output the second matching results determined at block 1020 bythe second signature comparator 525 performing the signature matchingprocedure with the second (e.g., long) analysis window 540.

At block 1045, the crediting facility 120 determines whether processingof the sequence of monitored media signatures accessed at block 1005 iscomplete. If signature processing is not complete (block 1045),processing returns to block 1005 and blocks subsequent thereto to enablethe crediting facility 120 to continue to performing media monitoring byprocessing the monitored media signatures. Otherwise, execution of theexample program 1000 ends.

An example program 1100 that may be executed to implement the examplecrediting facility 120 of FIGS. 1 and/or 9 is represented by theflowchart shown in FIG. 11. For convenience, and without loss ofgenerality, execution of the example program 1100 is described from theperspective of the example crediting facility 120 of FIG. 9 operating inthe example media monitoring system 100 of FIG. 1. With reference to thepreceding figures and associated written descriptions, the exampleprogram 1100 of FIG. 11 begins execution at block 1105 at which theexample signature comparator 925 of the crediting facility 120 accesses,from the example monitored signature storage 520, a sequence ofmonitored media signatures to be processed. At block 1110, the examplesignature comparator 925 accesses, from the example reference signaturestorage 510, sequences of reference media signatures to be compared withthe sequence of monitored media signatures accessed at block 1105. Asdescribed above, the sequences of reference media signatures accessed atblock 1110 are representative of respective different reference mediasources, one of which the crediting facility 120 will attempt toidentify as the source of the monitored media represented by thesequence of monitored media signatures.

At block 1115, the example matching results selector 945 of thecrediting facility 120 configures the signature comparator 925 toperform, as described above, a signature matching procedure with thefirst (e.g., short) example analysis window 535 on the sequence ofmonitored media signatures accessed at block 1105 to compare thosemonitored signatures with the respective sequences of reference mediasignatures accessed at block 1110. As described above, the first (e.g.,short) analysis window 535 defines the sizes (e.g., in time, in numberof signatures, etc.) of the neighborhood of the sequence of monitoredmedia signatures to be compared by the first signature comparator 525with neighborhoods of the respective ones of the reference mediasequences to determine respective signature matching resultscorresponding to each comparison instant of time (e.g., corresponding tothe time resolution of the matching results, such a matching resultbeing determined for each monitored signature packet, as describedabove).

At block 1200, the matching results selector 945 determines, asdescribed above, whether the first matching results output by thesignature comparator 925 at block 1115, which correspond to performingthe signature matching procedure with the first (e.g., short) analysiswindow 535, are indicative of a matching uncertainty condition. Examplemachine readable instructions capable of implementing the processing atblock 1200 are illustrated in FIG. 12, which is described in furtherdetail below. If the matching results selector 945 does not detect amatching uncertainty condition when evaluating the first matchingresults corresponding to the first (e.g., short) analysis window 535(block 1125), processing proceeds to block 1130 at which the matchingresults selector 545 continues to permit the first signature comparator525 to perform the signature matching procedure with the first (e.g.,short) analysis window 535, which causes the crediting facility 120 tooutput the first matching results corresponding to the first (e.g.,short) analysis window 535.

However, if the matching results selector 945 does detect a matchinguncertainty condition when evaluating the first matching resultscorresponding to the first (e.g., short) analysis window 535 (block1125), processing proceeds to block 1135 at which the matching resultsselector 545 configures the signature comparator 925 to perform, asdescribed above, the signature matching procedure with the second (e.g.,long) example analysis window 540 on the sequence of monitored mediasignatures accessed at block 1105 to compare those monitored signatureswith the respective sequences of reference media signatures accessed atblock 1110. At block 1140, the crediting facility 120 outputs the secondmatching results determined at block 1135 by the signature comparator925 performing the signature matching procedure with the second (e.g.,long) analysis window 540.

At block 1145, the crediting facility 120 determines whether processingof the sequence of monitored media signatures accessed at block 1105 iscomplete. If signature processing is not complete (block 1145),processing returns to block 1105 and blocks subsequent thereto to enablethe crediting facility 120 to continue to performing media monitoring byprocessing the monitored media signatures. Otherwise, execution of theexample program 1100 ends.

An example program 1200 capable of performing matching uncertaintydetection processing at blocks 1200 of FIGS. 10 and/or 11 is illustratedin FIG. 12. The example program 1200 of FIG. 12 is capable of beingexecuted by either the example matching results selector 545 of thecrediting facility 120 of FIG. 5, or the example matching resultsselector 945 of the crediting facility 120 of FIG. 9. Thus, forconvenience, the program 1200 is described as being executed by thematching results selector 545/945 to indicate that the program can beexecuted by either the matching results selector 545 or the matchingresults selector 945.

Turning to FIG. 12, execution of the example program 1200 begins atblock 1205 at which the matching results selector 545/945 accesses firstsignature matching results determined with the first (e.g., short)analysis window 535 (e.g., by the first signature comparator 525 or thesignature comparator 925). At block 1210, the matching results selector545/945 examines the reference timestamps associated with consecutiveones of the first matching results within an observation time period. Asdescribed above, at block 1215, the matching results selector 545/945determines whether any one or more of the consecutive timestamps arediscontinuous (e.g., whether one or more of the reference timestamps donot increment relative to preceding ones of the reference timestamps bya first amount within a range based on a time resolution associated withthe examined matching results).

If the matching results selector 545/945 detects discontinuity in theconsecutive timestamps (block 1215), processing proceeds to block 1220at which the matching results selector 545/945 indicates a matchinguncertainty condition has been detected. In some examples, if thematching results selector 545/945 does not detect discontinuity in theconsecutive timestamps (block 1215), processing proceeds to block 1225at which the matching results selector 545/945 examines the intermediatesignature comparison decisions made for each of the signature matchingresults. For example, at block 1230, for a given signature matchingresult, the matching results selector 545/945 examines, as describedabove, the intermediate signature comparison values determined whencomparing the given neighborhood of monitored media signatures to theneighborhoods of respective reference media signatures representative ofthe different reference media sources. If the matching results selector545/945 determines that multiple intermediate signature comparisonvalues satisfy a comparison threshold, processing proceeds to block 1220at which the matching results selector 545/945 indicates a matchinguncertainty condition has been detected. Otherwise, processing proceedsto block 1240 at which the matching results selector 545/945 continuesto examine the intermediate signature comparison decisions made for eachof the signature matching results. If after examining the intermediatesignature comparison decisions made for each of the signature matchingresults the matching results selector 545/945 determines that none ofthe results had multiple intermediate signature comparison decisionsthat satisfied the comparison threshold, processing proceeds to block1245 at which the matching results selector 545/945 indicates a matchinguncertainty condition has not been detected. Execution of the exampleprogram 1200 then ends.

FIG. 13 is a block diagram of an example processor platform 1300 capableof executing the instructions of FIGS. 10 and/or 12 to implement theexample crediting facility 120 of FIG. 5. The processor platform 1300can be, for example, a server, a personal computer, a mobile device(e.g., a cell phone, a smart phone, a tablet such as an iPad™), apersonal digital assistant (PDA), an Internet appliance, or any othertype of computing device.

The processor platform 1300 of the illustrated example includes aprocessor 1312. The processor 1312 of the illustrated example ishardware. For example, the processor 1312 can be implemented by one ormore integrated circuits, logic circuits, microprocessors or controllersfrom any desired family or manufacturer. In the illustrated example ofFIG. 13, the processor 1312 includes one or more example processingcores 1315 configured via example instructions 1332, which include theexample instructions of FIGS. 10 and/or 12, to implement the firstexample signature comparator 525, the second example signaturecomparator 530, the first example analysis window 535, the secondexample analysis window 540 and/or the example matching results selector545 of FIG. 5.

The processor 1312 of the illustrated example includes a local memory1313 (e.g., a cache). The processor 1312 of the illustrated example isin communication with a main memory including a volatile memory 1314 anda non-volatile memory 1316 via a link 1318. The link 1318 may beimplemented by a bus, one or more point-to-point connections, etc., or acombination thereof. The volatile memory 1314 may be implemented bySynchronous Dynamic Random Access Memory (SDRAM), Dynamic Random AccessMemory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or anyother type of random access memory device. The non-volatile memory 1316may be implemented by flash memory and/or any other desired type ofmemory device. Access to the main memory 1314, 1316 is controlled by amemory controller.

The processor platform 1300 of the illustrated example also includes aninterface circuit 1320. The interface circuit 1320 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a PCI express interface.

In the illustrated example, one or more input devices 1322 are connectedto the interface circuit 1320. The input device(s) 1322 permit(s) a userto enter data and commands into the processor 1312. The input device(s)can be implemented by, for example, an audio sensor, a microphone, acamera (still or video), a keyboard, a button, a mouse, a touchscreen, atrack-pad, a trackball, a trackbar (such as an isopoint), a voicerecognition system and/or any other human-machine interface. Also, manysystems, such as the processor platform 1300, can allow the user tocontrol the computer system and provide data to the computer usingphysical gestures, such as, but not limited to, hand or body movements,facial expressions, and face recognition.

One or more output devices 1324 are also connected to the interfacecircuit 1320 of the illustrated example. The output devices 1324 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay, a cathode ray tube display (CRT), a touchscreen, a tactileoutput device, a printer and/or speakers). The interface circuit 1320 ofthe illustrated example, thus, typically includes a graphics drivercard, a graphics driver chip or a graphics driver processor.

The interface circuit 1320 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network1326 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.). Inthe illustrated example of FIG. 13, the interface circuit 1320 is alsostructured to implement the example reference interface 505 and/or theexample monitor interface 515 of FIG. 5.

The processor platform 1300 of the illustrated example also includes oneor more mass storage devices 1328 for storing software and/or data.Examples of such mass storage devices 1328 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, RAID(redundant array of independent disks) systems, and digital versatiledisk (DVD) drives. In some examples, the mass storage device 1328 mayimplement the example reference signature storage 510 and/or the examplemonitored signature storage 520 of FIG. 5. Additionally oralternatively, in some examples the volatile memory 1314 may implementthe example reference signature storage 510 and/or the example monitoredsignature storage 520 of FIG. 5.

Coded instructions 1332 corresponding to the instructions of FIGS. 10and/or 12 may be stored in the mass storage device 1328, in the volatilememory 1314, in the non-volatile memory 1316, in the local memory 1313and/or on a removable tangible computer readable storage medium, such asa CD or DVD 1336.

FIG. 14 is a block diagram of an example processor platform 1400 capableof executing the instructions of FIGS. 11 and/or 12 to implement theexample crediting facility 120 of FIG. 9. The processor platform 1400can be, for example, a server, a personal computer, a mobile device(e.g., a cell phone, a smart phone, a tablet such as an iPad™), apersonal digital assistant (PDA), an Internet appliance, or any othertype of computing device.

The processor platform 1400 of the illustrated example includes aprocessor 1412. The processor 1412 of the illustrated example ishardware. For example, the processor 1412 can be implemented by one ormore integrated circuits, logic circuits, microprocessors or controllersfrom any desired family or manufacturer. In the illustrated example ofFIG. 14, the processor 1412 includes one or more example processingcores 1415 configured via example instructions 1432, which include theexample instructions of FIGS. 11 and/or 12, to implement the examplesignature comparator 925, the first example analysis window 535, thesecond example analysis window 540 and/or the example matching resultsselector 945 of FIG. 9.

The processor 1412 of the illustrated example includes a local memory1413 (e.g., a cache). The processor 1412 of the illustrated example isin communication with a main memory including a volatile memory 1414 anda non-volatile memory 1416 via a link 1418. The link 1418 may beimplemented by a bus, one or more point-to-point connections, etc., or acombination thereof. The volatile memory 1414 may be implemented bySynchronous Dynamic Random Access Memory (SDRAM), Dynamic Random AccessMemory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or anyother type of random access memory device. The non-volatile memory 1416may be implemented by flash memory and/or any other desired type ofmemory device. Access to the main memory 1414, 1416 is controlled by amemory controller.

The processor platform 1400 of the illustrated example also includes aninterface circuit 1420. The interface circuit 1420 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a PCI express interface.

In the illustrated example, one or more input devices 1422 are connectedto the interface circuit 1420. The input device(s) 1422 permit(s) a userto enter data and commands into the processor 1412. The input device(s)can be implemented by, for example, an audio sensor, a microphone, acamera (still or video), a keyboard, a button, a mouse, a touchscreen, atrack-pad, a trackball, a trackbar (such as an isopoint), a voicerecognition system and/or any other human-machine interface. Also, manysystems, such as the processor platform 1300, can allow the user tocontrol the computer system and provide data to the computer usingphysical gestures, such as, but not limited to, hand or body movements,facial expressions, and face recognition.

One or more output devices 1424 are also connected to the interfacecircuit 1420 of the illustrated example. The output devices 1424 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay, a cathode ray tube display (CRT), a touchscreen, a tactileoutput device, a printer and/or speakers). The interface circuit 1420 ofthe illustrated example, thus, typically includes a graphics drivercard, a graphics driver chip or a graphics driver processor.

The interface circuit 1420 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network1426 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.). Inthe illustrated example of FIG. 14, the interface circuit 1420 is alsostructured to implement the example reference interface 505 and/or theexample monitor interface 515 of FIG. 9.

The processor platform 1400 of the illustrated example also includes oneor more mass storage devices 1428 for storing software and/or data.Examples of such mass storage devices 1428 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, RAID(redundant array of independent disks) systems, and digital versatiledisk (DVD) drives. In some examples, the mass storage device 1428 mayimplement the example reference signature storage 510 and/or the examplemonitored signature storage 520 of FIG. 9. Additionally oralternatively, in some examples the volatile memory 1414 may implementthe example reference signature storage 510 and/or the example monitoredsignature storage 520 of FIG. 9.

Coded instructions 1432 corresponding to the instructions of FIGS. 11and/or 12 may be stored in the mass storage device 1428, in the volatilememory 1414, in the non-volatile memory 1416, in the local memory 1413and/or on a removable tangible computer readable storage medium, such asa CD or DVD 1436.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. An apparatus to perform signature comparison, theapparatus comprising: memory; and at least one processor to executecomputer readable instructions to at least: compare, based on a firstanalysis window, first groups of monitored signatures from a sequence ofmonitored signatures representative of monitored media with secondgroups of reference signatures from respective sequences of referencesignatures representative of corresponding different reference media todetermine a first sequence of signature match results for an observationperiod, the first groups and the second groups to have a first sizecorresponding to a first number of signatures; detect a discontinuity inthe first sequence of signature match results; and in response to thediscontinuity, compare, based on a second analysis window, third groupsof monitored signatures from the sequence of monitored signatures withfourth groups of reference signatures from the respective sequences ofreference signatures to determine a second sequence of signature matchresults for the observation period, the second analysis windowcorresponding to a longer duration of time than the first analysiswindow to cause the third groups and the fourth groups to have a secondsize corresponding to a second number of signatures greater than thefirst number of signatures.
 2. The apparatus of claim 1, wherein thediscontinuity corresponds to discontinuous timestamps included in thefirst sequence of signature match results.
 3. The apparatus of claim 1,wherein the first sequence of signature match results includes a firstsignature match result and a preceding second signature match result,the first signature match result includes a first timestamp, the secondsignature match result includes a second timestamp, and the at least oneprocessor is to detect the discontinuity when the first timestamp doesnot increment relative to the second timestamp by an amount within arange, the range based on a time resolution.
 4. The apparatus of claim3, wherein the sequence of monitored signatures includes packets ofmonitored signatures reported by a meter, the meter to generate thepackets of monitored signatures from the monitored media, the timeresolution based on a media duration represented by one of the packetsof monitored signatures.
 5. The apparatus of claim 1, wherein theprocessor is to detect the discontinuity based on whether at least onematch result in the first sequence of signature match results indicatesno match was found.
 6. The apparatus of claim 1, wherein the processoris to detect the discontinuity based on whether at least a portion ofthe first sequence of signature match results oscillates between atleast two different reference media identifiers.
 7. The apparatus ofclaim 1, wherein the processor is to output the second sequence ofsignature match results.
 8. At least one non-transitory computerreadable medium comprising computer readable instructions that, whenexecuted, cause at least one processor to at least: compare, based on afirst analysis window, first groups of monitored signatures from asequence of monitored signatures representative of monitored media withsecond groups of reference signatures from respective sequences ofreference signatures representative of corresponding different referencemedia to determine a first sequence of signature match results for anobservation period, the first groups and the second groups to have afirst size corresponding to a first number of signatures; detect adiscontinuity in the first sequence of signature match results; and inresponse to the discontinuity, compare, based on a second analysiswindow, third groups of monitored signatures from the sequence ofmonitored signatures with fourth groups of reference signatures from therespective sequences of reference signatures to determine a secondsequence of signature match results for the observation period, thesecond analysis window corresponding to a longer duration of time thanthe first analysis window to cause the third groups and the fourthgroups to have a second size corresponding to a second number ofsignatures greater than the first number of signatures.
 9. The at leastone non-transitory computer readable medium of claim 8, wherein thediscontinuity corresponds to discontinuous timestamps included in thefirst sequence of signature match results.
 10. The at least onenon-transitory computer readable medium of claim 8, wherein the firstsequence of signature match results includes a first signature matchresult and a preceding second signature match result, the firstsignature match result includes a first timestamp, the second signaturematch result includes a second timestamp, the instructions cause the atleast one processor to detect the discontinuity when the first timestampdoes not increment relative to the second timestamp by an amount withina range, the range based on a time resolution.
 11. The at least onenon-transitory computer readable medium of claim 10, wherein thesequence of monitored signatures includes packets of monitoredsignatures reported by a meter, the meter to generate the packets ofmonitored signatures from the monitored media, the time resolution basedon a media duration represented by one of the packets of monitoredsignatures.
 12. The at least one non-transitory computer readable mediumof claim 8, wherein the instructions cause the at least one processor todetect the discontinuity based on whether at least one match result inthe first sequence of signature match results indicates no match wasfound.
 13. The at least one non-transitory computer readable medium ofclaim 8, wherein the instructions cause the at least one processor todetect the discontinuity based on whether at least a portion of thefirst sequence of signature match results oscillates between at leasttwo different reference media identifiers.
 14. The at least onenon-transitory computer readable medium of claim 8, wherein theinstructions cause the at least one processor to output the secondsequence of signature match results.
 15. A method to perform signaturecomparison, the method comprising: comparing, by executing aninstruction with at least one processor, and based on a first analysiswindow, first groups of monitored signatures from a sequence ofmonitored signatures representative of monitored media with secondgroups of reference signatures from respective sequences of referencesignatures representative of corresponding different reference media todetermine a first sequence of signature match results for an observationperiod, the first groups and the second groups to have a first sizecorresponding to a first number of signatures; detecting a discontinuityin the first sequence of signature match results; and in response to thediscontinuity, comparing, by executing an instruction with the at leastone processor, and based on a second analysis window, third groups ofmonitored signatures from the sequence of monitored signatures withfourth groups of reference signatures from the respective sequences ofreference signatures to determine a second sequence of signature matchresults for the observation period, the second analysis windowcorresponding to a longer duration of time than the first analysiswindow to cause the third groups and the fourth groups to have a secondsize corresponding to a second number of signatures greater than thefirst number of signatures.
 16. The method of claim 15, wherein thefirst sequence of signature match results includes a first signaturematch result and a preceding second signature match result, the firstsignature match result includes a first timestamp, the second signaturematch result includes a second timestamp, and the detecting of thediscontinuity includes detecting the discontinuity when the firsttimestamp does not increment relative to the second timestamp by anamount within a range, the range based on a time resolution.
 17. Themethod of claim 16, wherein the sequence of monitored signaturesincludes packets of monitored signatures reported by a meter, the meterto generate the packets of monitored signatures from the monitoredmedia, the time resolution based on a media duration represented by oneof the packets of monitored signatures.
 18. The method of claim 15,wherein the detecting of the discontinuity is based on whether at leastone match result in the first sequence of signature match resultsindicates no match was found.
 19. The method of claim 15, wherein thedetecting of the discontinuity is based on whether at least a portion ofthe first sequence of signature match results oscillates between atleast two different reference media identifiers.
 20. The method of claim15, further including outputting the second sequence of signature matchresults.